Wafer support for chemical mechanical planarization

ABSTRACT

The present invention provides an improved planarization apparatus for chemical mechanical planarization. In an exemplary embodiment, the invention provides an apparatus having a back support operatively coupled to the edge support, the back support having at least one surface for supporting a back side of the object during planarization. The surface for supporting the back side provides a substantially friction free interface between the surface and the back side of the object to allow the object to move across the surface of the back support. In some embodiments, an edge support is movably coupled to an edge of an object for supporting and positioning the object during planarization.

The present application is based on and claims the benefit of U.S.Provisional Patent Application No. 60/161,705, filed Oct. 27, 1999, theentire disclosure of which is incorporated herein by reference.

BACKGROUND OF THE INVENTION

The present invention relates to the manufacture of electronic devices.More particularly, the invention provides a device for planarizing afilm of material of an article such as a semiconductor wafer. In anexemplary embodiment, the present invention provides an improvedsubstrate support for the manufacture of semiconductor integratedcircuits. However, it will be recognized that the invention has a widerrange of applicability; it can also be applied to flat panel displays,hard disks, raw wafers, MEMS wafers, and other objects that require ahigh degree of planarity.

The fabrication of integrated circuit devices often begins by producingsemiconductor wafers cut from an ingot of single crystal silicon whichis formed by pulling a seed from a silicon melt rotating in a crucible.The ingot is then sliced into individual wafers using a diamond cuttingblade. Following the cutting operation, at least one surface (processsurface) of the wafer is polished to a relatively flat, scratch-freesurface. The polished surface area of the wafer is first subdivided intoa plurality of die locations at which integrated circuits (IC) aresubsequently formed. A series of wafer masking and processing steps areused to fabricate each IC. Thereafter, the individual dice are cut orscribed from the wafer and individually packaged and tested to completethe device manufacture process.

During IC manufacturing, the various masking and processing stepstypically result in the formation of topographical irregularities on thewafer surface. For example, topographical surface irregularities arecreated after metallization, which includes a sequence of blanketing thewafer surface with a conductive metal layer and then etching awayunwanted portions of the blanket metal layer to form a metallizationinterconnect pattern on each IC. This problem is exacerbated by the useof multilevel interconnects.

A common surface irregularity in a semiconductor wafer is known as astep. A step is the resulting height differential between the metalinterconnect and the wafer surface where the metal has been removed. Atypical VLSI chip on which a first metallization layer has been definedmay contain several million steps, and the whole wafer may containseveral hundred ICs.

Consequently, maintaining wafer surface planarity during fabrication isimportant. Photolithographic processes are typically pushed close to thelimit of resolution in order to create maximum circuit density. Typicaldevice geometries call for line widths on the order of 0.5 μm. Sincethese geometries are photolithographically produced, it is importantthat the wafer surface be highly planar in order to accurately focus theillumination radiation at a single plane of focus to achieve preciseimaging over the entire surface of the wafer. A wafer surface that isnot sufficiently planar, will result in structures that are poorlydefined, with the circuits either being nonfunctional or, at best,exhibiting less than optimum performance. To alleviate these problems,the wafer is “planarized” at various points in the process to minimizenon-planar topography and its adverse effects. As additional levels areadded to multilevel-interconnection schemes and circuit features arescaled to submicron dimensions, the required degree of planarizationincreases. As circuit dimensions are reduced, interconnect levels mustbe globally planarized to produce a reliable, high density device.Planarization can be implemented in either the conductor or thedielectric layers.

In order to achieve the degree of planarity required to produce highdensity integrated circuits, chemical-mechanical planarization processes(“CMP”) are being employed with increasing frequency. A conventionalrotational CMP apparatus includes a wafer carrier for holding asemiconductor wafer. A soft, resilient pad is typically placed betweenthe wafer carrier and the wafer, and the wafer is generally held againstthe resilient pad by a partial vacuum. The wafer carrier is designed tobe continuously rotated by a drive motor. In addition, the wafer carriertypically is also designed for transverse movement. The rotational andtransverse movement is intended to reduce variability in materialremoval rates over the surface of the wafer. The apparatus furtherincludes a rotating platen on which is mounted a polishing pad. Theplaten is relatively large in comparison to the wafer, so that duringthe CMP process, the wafer may be moved across the surface of thepolishing pad by the wafer carrier. A polishing slurry containingchemically-reactive solution, in which are suspended abrasive particles,is deposited through a supply tube onto the surface of the polishingpad.

CMP is advantageous because it can be performed in one step, in contrastto past planarization techniques which are complex, involving multiplesteps. Moreover, CMP has been demonstrated to maintain high materialremoval rates of high surface features and low removal rates of lowsurface features, thus allowing for uniform planarization. CMP can alsobe used to remove different layers of material and various surfacedefects. CMP thus can improve the quality and reliability of the ICsformed on the wafer.

Chemical-mechanical planarization is a well developed planarizationtechnique. The underlying chemistry and physics of the method isunderstood. However, it is commonly accepted that it still remains verydifficult to obtain smooth results near the center of the wafer. Theresult is a planarized wafer whose center region may or may not besuitable for subsequent processing. Sometimes, therefore, it is notpossible to fully utilize the entire surface of the wafer. This reducesyield and subsequently increases the per-chip manufacturing cost.Ultimately, the consumer suffers from higher prices.

It is therefore desirable to improve the useful surface of asemiconductor wafer to increase chip yield. What is needed is animprovement of the CMP technique to improve the degree of globalplanarity that can be achieved using CMP.

SUMMARY OF THE INVENTION

The present invention achieves these benefits in the context of knownprocess technology and known techniques in the art. The presentinvention provides an improved planarization apparatus for chemicalmechanical planarization. Specifically, the present invention providesan improved planarization apparatus that precisely aligns an object forplanarization and eliminates deformation of the object duringplanarization.

In an exemplary embodiment, the invention provides an apparatus havingan edge support movably coupled to an edge of an object for supportingand positioning the object during planarization; a back supportoperatively coupled to the edge support, the back support having atleast one surface for supporting a back side of the object duringplanarization. The surface for supporting the back side provides asubstantially friction free interface between the surface and the backside of the object to allow the object to move across the surface of theback support.

In another specific embodiment, the invention can have a polishing headoperatively coupled to the back support, the polishing head comprising apolishing pad, the polishing pad having a treatment surface and a centeraxis, the polishing head being rotatably coupled to a drive motor torotate the treatment surface about the center axis to polish the object.

In another specific embodiment, the invention can have a driveoperatively coupled to the edge support to rotate the object in a fixedplane on the back support during planarization, the fixed plane beingsubstantially parallel to a treatment surface of a polishing pad.Alternatively, the invention can have a drive operatively coupled to theedge support, the object having a center axis, wherein the edge supportrotates the object about its center axis in a fixed plane duringplanarization, the fixed plane being substantially parallel to atreatment surface of a polishing pad.

In the specific embodiments, the edge support can move the object in apredetermined pattern relative to the polishing pad, the pattern beingin a fixed plane at least when a polishing pad contacts the objectduring planarization, the fixed plane being substantially parallel to atreatment surface of a polishing pad. The predetermined pattern issubstantially radial, linear, continuous, discontinuous, or anycombination thereof.

In another specific embodiment the edge support can have a plurality ofrollers, the object and each of the rollers having a center axis, eachof the rollers being movably coupled to the edge of the object such thatat least one of the rollers rotates about its center axis to drive theobject to rotate about its center axis. At least one of the rollersrotates about its center axis in a to drive the object to rotate aboutits center axis in a counterclockwise direction. Alternatively, the edgesupport can rotate about its center axis of the object thereby causingthe object to rotate about the center axis of the edge support.

In a specific embodiment, a surface of the back support comprises adiameter that is substantially the same size as the polishing paddiameter for providing adequate support to the object duringplanarization. The back support can be an air bearing, a liquid bearing,or the equivalent. In the present invention, the back support tracks apolishing pad to provide support to the object during planarization.This prevents deformation of the object during planarization. A furtherunderstanding of the nature and advantages of the present invention maybe realized by reference to the latter portions of the specification andattached drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a simplified diagram of a planarization apparatus according toan embodiment of the present invention;

FIG. 1A is a simplified top-view diagram of a carousel for supportingmultiple guide and spin assemblies according to an embodiment of thepresent invention;

FIG. 2 is a detailed diagram of a guide and spin roller according to anembodiment of the present invention;

FIG. 2A is a diagram of a guide and spin roller according to anotherembodiment of the present invention;

FIG. 3 is a detailed diagram of a polish pad back support according toan embodiment of the present invention;

FIG. 3A is a simplified diagram of a support mechanism for supportingthe wafer with projected gimbal points according to an embodiment of thepresent invention;

FIG. 3B is a top plan view of a gimbal drive support for the polishingpad with project gimbal point;

FIG. 3C is a cross-sectional view of the gimbal drive support of FIG. 3Balong 1—1;

FIG. 3D is a cross-sectional view of the gimbal drive support of FIG. 3Balong 2—2;

FIG. 3E is an exploded perspective view of the gimbal drive support ofFIG. 3B

FIG. 4 is a simplified top-view diagram of a planarization apparatusaccording to an embodiment of the present invention;

FIG. 4A is a simplified top-view diagram of the polishing pad andspindle illustrating spin and orbit rotations;

FIG. 5 is an alternative diagram of a planarization apparatus accordingto another embodiment of the present invention; and

FIG. 6 is a simplified block diagram of a planarization calibrationsystem of the present invention.

DESCRIPTION OF THE SPECIFIC EMBODIMENTS

FIG. 1 is a simplified diagram of a planarization apparatus 100according to an embodiment of the present invention. This diagram ismerely an example, which should not limit the scope of the claimsherein. One of ordinary skill in the art would recognize many othervariations, modifications, and alternatives. In a specific embodiment,planarization apparatus 100 is a chemical-mechanical planarizationapparatus.

Guide and Spin Assembly

The apparatus 100 includes an edge support, or a guide and spin assembly110, that couples to the edge of an object, or a wafer 115. While theobject in this specific embodiment is a wafer, the object can be otheritems such as a in-process wafer, a coated wafer, a wafer comprising afilm, a disk, a panel, etc. Guide assembly 110 supports and positionswafer 115 during a planarization process. FIG. 1 also shows a polishingpad assembly 116 having a polishing pad 117, and a back-support 118attached to a dual arm 119. Pad assembly 116, back support 117, dual arm118 is described in detail below.

In a specific embodiment, guide assembly 110 includes rollers 120, eachof which couples to the edge of wafer 115 to secure it in positionduring planarization. The embodiment of FIG. 1 shows three rollers. Theactual number of rollers, however, will depend on various factors suchas the shape and size of each roller, the shape and size of the wafer,and nature of the roller-wafer contact, etc. Also, at least one of therollers 120 drives the wafer 115, that is, cause the wafer to rotate, orspin. The rest can serve as guides, providing support as the wafer ispolished. The rollers 120 are positioned at various points along thewafer perimeter. As shown in FIG. 1, the rollers 120 attach to the wafer115 at equidistant points along the wafer perimeter. The rollers 120 canbe placed anywhere along the wafer perimeter. The distance between eachroller will depend on the number of rollers, and on other factorsrelated to the specific application.

The embodiment of FIG. 1 shows one guide and spin assembly 110. Theactual number of such assemblies will depend on the specificapplication. For example, FIG. 1A shows a simplified top-view diagram ofa carousel 121 for supporting multiple guide and spin assemblies 110 forprocessing multiple wafers 115 according to an embodiment of the presentinvention. In this specific embodiment, the carousel (FIG. 1A) can beused with multiple guide assemblies for planarizing many wafers. Theactual size, shape, and configuration of the carousel will depend on thespecific application. Also, when multiple guide assemblies are used, allguide assemblies need not be configured identically. The configurationof each guide assembly will depend on the specific application. Forhigher throughput, wafers are mounted onto the guide assemblies that arein cue during the planarization of one or more of the other wafers. Foreven higher throughput, such wafer carousels are configured tooperatively couple to multiple planarization apparatus.

FIG. 2 is a detailed diagram of a roller 120 of FIG. 1 according to anembodiment of the present invention. This diagram is merely an example,which should not limit the scope of the claims herein. One of ordinaryskill in the art would recognize many other variations, modifications,and alternatives. As shown, each roller 120 has a base portion 125, atop portion 130, and an annular notch 131 extending completely aroundthe roller, and positioned between the base and top portions. The depthand shape of notch 131 will vary depending on the purpose of thespecific roller. A roller designated to drive the rotation of the wafermight have a deeper notch to provide for more surface area contact withthe wafer 115. Alternatively, a roller designated to merely guide thewafer might have a shallower notch, having enough depth to provideadequate support.

FIG. 2A shows another roller 120 a having a base portion 125 a similarto the base portion 125 of FIG. 2. The top portion 130 a has a smallercross-section that the top portion 130 of FIG. 2, and desirably includesa tapered or inclined surface 132 a tapering down to an annular notch131 a which is more shallow than the notch 131 of FIG. 2. The shallownotch 131 a is sufficient to connect the roller 120 a to the edge of thewafer 115. The top portion 130 a and the shallow notch 131 a make theengagement of the roller 120 a with the edge of the wafer 115 easier.The replacement of the wafer 115 can also be performed more readily andquickly since the roller 120 a with the smaller to portion 130 a neednot be retracted as far as the roller 120 of FIG. 2. The surface 133 aof the bottom portion 125 a may also be inclined by a small degree(e.g., about 1-5°) as indicated by the broken line 133 b to furtherfacilitate wafer engagement.

The edge of wafer 115 is positioned in the notch of each roller suchthat the process side of wafer 115 faces polishing pad 117. To securewafer 115, the base portion of each roller provides an upward force 140against the back side 150 of the wafer while the top portion provides adownward force 160 against the process surface 170 (side to be polished)of the wafer. For additional support, the inner wall 171 of the notchprovides an inward force 190 against the wafer edge. The top and baseportions 130, 125 constitute one piece. Alternatively, the top and baseportions 130, 125 can include multiple pieces. For example, the topportion 130 can be a separate piece, such as a screw cap or otherfastening device or the equivalent. Each roller 120 has a center axis201 and each can rotate about its axis. Rotation can be clockwise orcounterclockwise. Rotation can also accelerate or decelerate.

Guide and spin assembly 110 also has a roller base (not shown) forsupporting the rollers. The size, shape, and configuration of the basewill depend on the actual configuration of the planarization apparatus.For example, the base can be a simple flat surface that is attached toor integral to the planarization apparatus. The base can support some ofthe rollers, while at least one roller need to be retractablesufficiently to permit insertion and removal of the wafer 115, and needto be adjustable relative to the edge of the wafer 115 to control theforce applied to the edge of the wafer 115.

In operation, during planarization, guide assembly 110 can move wafer115 in various ways relative to polishing pad 117. For example, theguide assembly can move the wafer laterally, or provide translationaldisplacement, in a fixed plane, the fixed plane being substantiallyparallel to a treatment surface of polishing pad 117 and back support118. The guide assembly can also rotate, or spin, the wafer in the fixedplane about the wafer's axis. As a result, the guide assembly 110translates the wafer 115 in the x-, y-, and z-directions, or acombination thereof. During actual planarization, that is when apolishing pad contacts the wafer, the guide assembly can move the waferlaterally in a fixed plane. The guide assembly can translate the waferin any number of predetermined patterns relative to the polishing pad.Such a predetermined pattern will vary and will depend on the specificapplication. For example, the pattern can be substantially radial,linear, etc. Also, at least when the polishing pad contacts the objectduring planarization, such a pattern can be continuous or discontinuousor a combination thereof.

Conventional translation mechanisms for x-, y-, z-translation cancontrol and traverse the guide assembly. For example, alternativemechanisms include pulley-driven devices and pneumatically operatedmechanisms. The guide assembly and the wafer can traverse relative tothe polishing pad in a variety of patterns. For example, the traversepath can be radial, linear, orbital, stepped, etc. or any combinationdepending on the specific application. The rotation direction of thewafer can be clockwise or counter clockwise. The rotation speed can alsoaccelerate or decelerate.

Still referring to FIG. 2, as indicated above, in addition to lateralmovement, the guide assembly can also rotate, or spin, wafer 115 in thefixed plane about the wafer center axis 202. The fixed plane issubstantially parallel to a treatment surface of polishing pad 117. Oneway to provide rotational movement is by using rollers 120 describedabove. As mentioned above, at least one roller rotates about its centeraxis to drive the wafer to rotate about its center axis. The otherrollers can also drive the wafer to rotate. They can also rotate freely.As said, each roller can rotate about its center axis 201 in either aclockwise or counterclockwise direction. The wafer will rotate in theopposite direction of the driving roller.

Specifically, as one or more of the driving rollers spin along theirrotational axis 201 during operation, the friction between the innerwalls of notch 131 and the wafer edge cause wafer 115 to rotate alongits own axis 202. The roller itself can provide the friction. Forexample, the notch can include ribs, ridges, grooves, etc.Alternatively, a layer of any known material having a sufficientfriction coefficient, such as a rubber or polyamide material, can alsoprovide friction. One of ordinary skill in the art would recognize manyother variations, modifications, and alternatives. For example, eachroller can be movably or immovably fixed to a base (not shown) and awheel within the notch of each roller can spin, causing the wafer tospin.

To rotate, or spin, the wafer, one or more conventional drive motors(not shown) or the equivalent can be operatively coupled to the wafer,rollers, or roller base. The drive can be coupled to one or more of therollers via a conventional drive belt (not shown) to spin the wafer.Alternatively, the drive can also couple to the guide assembly such thatthe entire guide assembly rotates about its center axis thereby causingthe wafer to rotate about the guide assembly center axis. With allembodiments, the motor can be reversible such that the rotationdirection 275 (FIG. 1) of the polishing pad 117 about its axis 270 canbe clockwise or counter clockwise. Drive motor can also be avariablespeed device to control the rotational speed of the pad. Also,the rotational speed of the pad can also accelerate or deceleratedepending on the specific application.

Alternatively, the edge support can also be stationary duringplanarization while a polishing pad rotates or moves laterally relativeto the wafer. This variation is described in more detail below. Duringplanarization, such movement occurs in the fixed plane at least when thepolishing pad 117 contacts the wafer. During any part of or during theentire planarization process, any combination of the movements describedabove is possible.

Referring to FIG. 1, planarization apparatus 100 also includes apolishing head, or polishing pad assembly 116, for polishing wafer 115.Pad assembly 116 includes polishing pad 117, a polishing pad chuck 250for securing and supporting polishing pad 117, and a polishing padspindle 260 coupled to chuck 250 for rotation of pad 117 about its axis270. According to a specific embodiment, the pad diameter issubstantially less than the wafer diameter, typically 20% of the waferdiameter.

To rotate, or spin, the wafer, one or more conventional drive motors(not shown) or the equivalent can be operatively coupled to polishingpad spindle 260 via a conventional drive belt (not shown). The motor canbe reversible such that the rotation direction 275 of polishing pad 117can be clockwise or counter clockwise. Drive motor can also be avariable-speed device to control the rotational speed of the polishingpad. Also, the rotational speed of the polishing pad can also accelerateor decelerate depending on the specific application.

Polishing and Back Support Assembly

The planarization apparatus also includes a base, or dual arm 119. Whilethe base can have any number of configurations, the specific embodimentshown is a dual arm. Pad assembly 116 couples to back support 118 viadual arm 119. Dual arm 119 has a first arm 310 for supporting padassembly 116 and a second arm 320 for supporting back support 118. Thearms 310, 320 may be configured to move together or, more desirably, canmove independently. The arms 310, 320 can be moved separately todifferent stations for changing pad or puck and facilitate ease ofassembling the components for the polishing operation.

According to a specific embodiment of the invention, back support 118tracks polishing pad 117 to provide support to wafer 115 duringplanarization. This can be accomplished with the dual arm. In a specificembodiment, the pad assembly 116 attaches to first arm 310 and backsupport 118 attaches to second arm 320. Dual arm 119 is configured toposition the pad assembly 116 and back support 118 such that a supportsurface of back support 118 faces the polishing pad 117 and such thatthe support surface of back support 118 and polishing pad 117 aresubstantially planar to one another. Also, according to the presentinvention, the centers of the polishing pad and surface of the backsupport are precisely aligned. This precision alignment allows forpredicable and precise planarization. Precision alignment is ensuredwhen the first and second arms constitute one piece. Alternatively, botharms can include multiple components and may be movable independently.As such, the components are substantially stable such that the precisionalignment is maintained.

Specifically, according to one embodiment, dual arm 119 supports padassembly 116 such that spindle 260 passes rotatably through first arm310 towards back support 118 which is supported by second arm 320. Therotational axis 270 of the pad 117 is equivalent to that of the spindle260. Rotational axis 270 is positioned to pass through back support 118,preferably through the center of the back support 118. Pad assembly 116is configured for motion in the direction of wafer 115. FIG. 1 shows theprocess surface of the wafer positioned substantially horizontally andfacing upwardly.

According to a specific embodiment of the present invention, the entireplanarization system can be configured to polish the wafer in a varietyof positions. During planarization, for example, the dual arm 119 can bepositioned such that the wafer 115 is controllably polished in ahorizontal position or a vertical position, or in any angle. Thesevariations are possible because the wafer 115 is supported by rollers120 rather than by gravity. Such flexibility is useful in, for example,a slurry-less polish system.

In operation, dual arm 119 can translate pad assembly 116 relative towafer 115 in a variety of ways. For example, the dual arm 119 can pivotabout the pivot shaft to traverse the pad 117 radially across the wafer115. In another embodiment, both arms 310 and 320 can extendtelescopically (not shown) to traverse the pad laterally linearly acrossthe wafer 115. Both radial and linear movements can also be combined tocreate a variety of traversal paths, or patterns, relative to the wafer115. Such patterns can be, for example, radial, linear, orbital,stepped, continuous, discontinuous, or any combination thereof. Theactual traverse path will of course depend on the specific application.

FIG. 3 is a detailed diagram of back support 118 of FIG. 1 according toan embodiment of the present invention. This diagram is merely anexample, which should not limit the scope of the claims herein. One ofordinary skill in the art would recognize many other variations,modifications, and alternatives. Back support 118 supports wafer 115during planarization. Specifically, back support 118 dynamically trackspolishing pad 117 to provide local support to wafer 115 duringplanarization. Such local support eliminates wafer deformation due tothe force of the polishing pad against the wafer during planarization.This also results in uniform polishing and thus planarity. In a specificembodiment, the back support 118 operatively couples to the pad assembly116 via the dual arm 119. In a specific embodiment, the back support 118is removably embedded in second arm 320 of the dual arm. Referring toFIG. 1, rotational axis 270 of polishing pad 117 and spindle 260 passthrough back support 118.

Referring back to FIG. 3, back support 118 can be configured in anynumber of ways for supporting wafer 115 during planarization. In aspecific embodiment, back support 118 has a flat portion, or supportsurface 350, that contacts the back side 150 of the wafer duringplanarization. The support surface 350 desirably provides asubstantially friction free interface between surface 350 and back side150 of the wafer by using a low-friction solid material such as Teflon.Alternatively, the support surface 350 may support a fluid bearing asthe frictionless interface with the back side 150. The fluid may be agas such as air or a liquid such as water, which may be beneficial forserving the additional function of cleaning the back side 150 of thewafer. This friction free interface allows the wafer to move across thesurface of the back support.

Support surface 350 is substantially planar with the wafer 115 and pad117. The diameter of the surface should be large enough to provideadequate support to the object during planarization. In a specificembodiment, the back support surface has a diameter that issubstantially the same size as the polishing pad diameter. In FIG. 3,the back support 118 shown is a spherical air bearing and has aspherical portion 340 allowing it to be easily inserted into second arm320. The rotation of the spherical portion 340 relative to the secondarm allows the back support 118 to track the polishing pad 117 andsupport the wafer 115 with the support surface 350. The back support 118in FIG. 3 has a protrusion 341 into a cavity of the second arm. Theprotrusion 341 may serve to limit the rotation of the back support 118relative to the second arm 320 during tracking of the polishing pad 117.In an alternate embodiment, the back support 118 may be generallyhemispherical without the protrusion.

The process surface 170 of the wafer 115 faces the pad 117 and the backside 150 of the wafer 115 faces the back support 118. Also, the wafer115 is substantially planar with both the pad 117 and back support 118.In another embodiment, the back support 118 can be replaced with asecond polishing pad assembly for double-sided polishing. In such anembodiment, the second pad assembly can be configured similarly to thefirst pad assembly on the first arm. The polishing pads of each aresubstantially planar to one another and to the wafer 115.

In a specific embodiment, the back support is a bearing. In thisspecific embodiment, the bearing can be a low-friction solid material(e.g., Teflon), an air bearing, a liquid bearing, or the equivalent. Thetype of bearing will depend on the specific application and types ofbearing available.

In the specific embodiment as shown in FIG. 1, the dual arm 119 is aC-shaped clamp having projected gimbal points that allow for flexing ofthe dual arm 119 and still keep the face of the wafer in good contactwith the polishing pad 117. The projected gimbal points are more clearlyillustrated in FIG. 3A. The polishing pad chuck 250 is supported by thefirst arm 310, and the back support 118 is supported by the second arm320. The polishing pad chuck 250 has a hemispherical surface 251centered about a pivot point or gimbal point 252 which preferably isdisposed at or near the upper surface of the wafer 115. Positioning thegimbal point 252 at or near the surface of the wafer 115 allows gimbalmotion or pivoting of the chuck 250 relative to the first arm 310without the problem of cocking. Cocking occurs when the projected gimbalpoint is above the wafer surface, and causes the forward end of thepolishing pad 117 to dig into the wafer surface at the forward edge andlift up at the rear edge. The cocking is inherently unstable.Positioning the project gimbal point on the wafer surface avoidscocking. If the gimbal point is projected below the surface of thewafer, friction between the polishing pad 117 and the wafer surfaceproduces a skiing effect which lifts the forward edge of the polishingpad 117 and causes the rear edge to dig into the wafer surface as thepolishing pad moves relative to the wafer surface. This is more stablethan cocking. The desirable maximum distance between the projectedgimbal point and the wafer surface depends on the size of the polishingpad 117. For example, the distance may be less than about 0.1 inch for apolishing pad having a diameter of about 1.5 inch. The distance isdesirably less than about 0.1 times, more desirably less than about 0.02times, the diameter of the polishing pad. Likewise, the sphericalsurface 340 of the back support 118 desirably has a projected pivotpoint 254 disposed at or near the lower surface of the wafer 115.

FIGS. 3B-3E show the gimbal mechanism coupling the polishing pad chuck250 with the first arm 310. The chuck 250 is connected to an inner cup256 which is connected to an outer cup 258 that is supported by thefirst arm 310 of the dual arm 119. A torsional drive motor may becoupled with the outer cup 258 to rotate the polishing pad 117 via thegimbal mechanism around the z-axis. A pair of inner drive pins 262extend from the chuck 250 into radial slots 264 provided in the innercup 256 and extending generally in the direction of the y-axis. Theradial slots 264 constrain the inner drive pins 262 in thecircumferential direction so that the chuck 250 moves with the inner cup256 in the circumferential direction around the z-axis. The inner drivepins 262 may move along the radial slots 264 to permit rotation of thechuck 250 relative to the inner cup 256 around the x-axis.

A pair of outer drive pins 266 extend from the inner cup 256 into radialslots 268 provided in the outer cup 258 and extending generally in thedirection of the x-axis. The radial slots 268 constrain the outer drivepins 266 in the circumferential direction so that the inner cup 256moves with the outer cup 258 in the circumferential direction around thez-axis. The outer drive pins 266 may move along the radial slots 268 topermit rotation of the inner cup 256 relative to the outer cup 258around the y-axis.

The hemispherical drive cups 256, 258 isolate two axes of motion toallow full gimbal of the gimbal mechanism about the gimbal point orpivot point 252. The gimbal mechanism allows transmission of thetorsional drive of the polishing pad 117 about the z-axis withoutinducing a torque moment on the polishing pad 117 at the interface withthe wafer surface to produce a skiing effect. The polishing pad 117becomes self-aligning with respect to the surface of the wafer 115 whichmay be offset from the x-y plane.

The gimbal mechanism shown in FIGS. 3B-3E is merely illustrative. Indifferent embodiments, the drive pins may be replaced by machinedprotrusions. Balls or rollers that fit into mating, crossing grooves maybe used to provide rolling contact with low friction between the movablemembers of the mechanism. Although the embodiment shown includes asingle track in the x-direction and a single track in the y-direction,additional tracks may be provided. The members of the assembly may haveother shapes different from the spherical members and still providegimbal movements or spherical drive motions. It is understood that otherways of supporting the wafer and of tracking the polishing pad may beemployed to provide the projected gimbal point at the desired location.

Planarization apparatus 100 operates as follows. Referring back to FIG.1, assembly 110 positions wafer 115 between polishing pad 117 and backsupport 118. The polishing pad is lowered onto the process surface 170of the wafer 115. Pad assembly 116 is driven by a conventional actuator(not shown), a piston-driven mechanism, for example, havingvariable-force control to control the downward pressure of the pad 117upon the process surface 170. The actuator is typically equipped with aforce transducer to provide a downforce measurement that can be readilyconverted to a pad pressure reading. Numerous pressure-sensing actuatordesigns, known in the relevant engineering arts, can be used. Of course,other types of actuator such as servo-motors and screw-drive linearmotors may be used instead.

FIG. 4 is a simplified top-view diagram of planarization apparatus 100according to an embodiment of the present invention. This diagram ismerely an example, which should not limit the scope of the claimsherein. One of ordinary skill in the art would recognize many othervariations, modifications, and alternatives. In a specific embodiment,dual arm 119 is configured to pivot about a pivot shaft 360 to providetranslational displacement of pad assembly 116, and polishing pad 117,relative to guide and spin assembly 110, and wafer 115. Pivot shaft 360is fixed to a planarization apparatus system (not shown).

The polishing pad spindle 260 may also rotate to rotate the polishingpad 117, as illustrated in FIG. 4A. In addition to the spin rotation 276about its own axis 270, the spindle 260 may also orbit about an orbitalaxis 277 in directions 278 to produce orbiting of the polishing pad 117as shown in broken lines. The orbital axis 277 is offset from the spinaxis 270 by a distance which may be selected based on the size of thewafer 115 and the size of the polishing pad 117. For instance, theoffset distance may range from about 0.01 inch to several inches. In aspecific example, the distance is about 0.25 inch. The orbital rotationis more clearly illustrated in FIG. 4A. Different motors may be used todrive the spindle 260 in spin and to drive the spindle 260 in orbitalrotation.

FIG. 5 is an alternative diagram of planarization apparatus 100according to another embodiment of the present invention. This diagramis merely an example, which should not limit the scope of the claimsherein. One of ordinary skill in the art would recognize many othervariations, modifications, and alternatives. In a specific embodiment, aslurry delivery mechanism 400 is provided to dispense a polishing slurry(not shown) onto the process surface of wafer 115 during planarization.Although FIG. 5 shows a single mechanism 400 or dispenser 400,additional dispensers may be provided depending on the polishingrequirements of the wafer. Polishing slurries are known in the art. Forexample, typical slurries include a mixture of colloidal silica ordispersed alumina in an alkaline solution such as KOH, NH₄OH or CeO₂.Alternatively, slurry-less pad systems can be used.

A splash shield 410 is provided to catch the polishing fluids and toprotect the surrounding equipment from the caustic properties of anyslurry that might be used during planarization. The shield material canbe polypropylene or stainless steel, or some other stable compound thatis resistant to the corrosive nature of polishing fluids. The slurry canbe dispose via a drain 420.

A controller 430 in communication with a data store 440 issues variouscontrol signals 450 to the foregoing-described components of theplanarization apparatus. The controller provides the sequencing controland manipulation signals to the mechanics to effectuate a planarizationoperation. The data store 440 can be externally accessible. This permitsuser-supplied data to be loaded into the data store 440 to provide theplanarization apparatus with the parameters for planarization. Thisaspect of the invention will be further discussed below.

Any of a variety of controller configurations is contemplated for thepresent invention. The particular configuration will depend onconsiderations such as throughput requirements, available footprint forthe apparatus, system features other than those specific to theinvention, implementation costs, and the like. In a specific embodiment,controller 430 is a personal computer loaded with control software. Thepersonal computer includes various interface circuits to each componentof apparatus 100. The control software communicates with thesecomponents via the interface circuits to control apparatus 100 duringplanarization. In this embodiment, data store 440 can be an internalhard drive containing desired planarization parameters. User-suppliedparameters can be keyed in manually via a keyboard (not shown).Alternatively, the data store 440 is a floppy drive in which case theparameters can be determined elsewhere, stored on a floppy disk, andcarried over to the personal computer. In yet another alternative, thedata store 440 is a remote disk server accessed over a local areanetwork. In still yet another alternative, the data store 440 is aremote computer accessed over the Internet; for example, by way of theworld wide web, via an FTP (file transfer protocol) site, and so on.

In another embodiment, controller 430 includes one or moremicrocontrollers that cooperate to perform a planarization sequence inaccordance with the invention. Data store 440 serves as a source ofexternally provided data to the microcontrollers so they can perform thepolish in accordance with user-supplied planarization parameters. Itshould be apparent that numerous configurations for providinguser-supplied planarization parameters are possible. Similarly, itshould be clear that numerous approaches for controlling the constituentcomponents of the planarization apparatus are possible.

Planarization Calibration System

FIG. 6 is a simplified block diagram of a planarization calibrationsystem of the present invention. It is noted that the figure is merely asimplified block diagram representation highlighting the components ofthe planarization apparatus of the present invention. The system shownis exemplary and should not unduly limit the scope of the claims herein.A person of ordinary skill in the relevant arts will recognize manyvariations, alternatives and modifications without departing from thescope and spirit of the invention. Planarization system 800 includes aplanarization station 804 for performing planarization operations.Planarization station 804 can use a network interface card (not shown)to interface with other system components, such as a wafer supply,measurement station, transport device, etc. There is a wafer supply 802for providing blank test wafers and for providing production wafers. Ameasurement station 806 is provided for making surface measurements fromwhich the removal profiles are generated. The planarization station 804,wafer supply 802 and measurement station 806 are operatively coupledtogether by a robotic transport device 808. A controller 810 includescontrol lines and data input lines 814 that cooperatively coupletogether the constituent components of system 800. Controller 810includes a data store 812 for storing at least certain user-suppliedplanarization parameters. Alternatively, data store 812 can be aremotely accessed data server available over a network in a local areanetwork.

Controller 810 can be a self-contained controller having a userinterface to allow a technician to interact with and control thecomponents of system 800. For example, controller 810 can be a PC-typecomputer having contained therein one or more software modules forcommunicating with and controlling the elements of system 800. Datastore 812 can be a hard drive coupled over a communication path 820,such as a data bus, for data exchange with controller 810.

In another configuration, a central controller (not shown) accessescontroller 810 over communication path 820. Such a configuration mightbe found in a fabrication facility where a centralized controller isresponsible for a variety of such controllers. Communication path 820might be the physical layer of a local area network. As can be seen, anyof a number of controller configurations is contemplated in practicingthe invention. The specific embodiment will depend on considerationssuch as the needs of the end-user, system requirements, system costs,and the like.

The system diagrammed in FIG. 6 can be operated in production mode or incalibration mode. During a production run, wafer supply 802 containsproduction wafers. During a calibration run, wafer supply 802 is loadedwith test wafers. Measurement station 806 is used primarily during acalibration run to perform measurements on polished test wafers toproduce removal profiles. However, measurement station 806 can also beused to monitor the quality of the polish operation during productionruns to monitor process changes over time.

In another embodiment, measurement system 806 can be integrated intoplanarization station 804. This arrangement provides in situ measurementof the planarization process. As the planarization progresses,measurements can be taken. These real time measurements allow forfine-tuning of the planarization parameters to provide higher degrees ofuniform removal of the film material.

The program code constituting the control software can be expressed inany of a number of ways. The C programming language is a commonly usedlanguage because many compilers exist for translating the high-levelinstructions of a C program to the corresponding machine language of thespecific hardware being used. For example, some of the software mayreside in a PC based processor. Other software may be resident in theunderlying controlling hardware of the individual stations, e.g.,planarization station 804 and measurement station 806. In such cases,the C programs would be compiled down to the machine language of themicrocontrollers used in those stations. In one specific embodiment, thesystem employs a PC-based local or distributed control scheme with softlogic programming control.

As an alternative to the C programming language, object-orientedprogramming languages can be used. For example, C++ is a commonobject-oriented programming language. The selection of a specificprogramming language can be made without departing from the scope andspirit of the present invention. Rather, the selection of a particularprogramming language is typically dependent on the availability of acompiler for the target hardware, the availability of related softwaredevelopment tools, and on the preferences of the software developmentteam.

While the above is a full description of the specific embodiments,various modifications, alternative constructions and equivalents knownto those of ordinary skill in the relevant arts may be used. Forexample, while the description above is in terms of a semiconductorwafer, it would be possible to implement the present invention withalmost any type of article having a surface or the like. Therefore, theabove description and illustrations should not be taken as limiting thescope of the present invention which is defined by the appended claims.

What is claimed is:
 1. A chemical-mechanical planarization apparatus forplanarizing objects, the apparatus comprising: an edge support movablycoupled to an edge of an object for supporting and positioning theobject during planarization; and a back support operatively coupled tothe edge support, the back support having at least one surface forsupporting a back side of the object during planarization, the surfaceproviding a substantially friction free interface between the surfaceand the back side of the object to allow the object to move across thesurface of the back support; and an edge support movably coupled to anedge of an object for supporting and positioning the object duringplanarization.
 2. The apparatus of claim 1 further comprising a driveoperatively coupled to the edge support to rotate the object in a fixedplane on the back support during planarization, the fixed plane beingsubstantially parallel to a treatment surface of a polishing pad.
 3. Theapparatus of claim 1 further comprising a drive operatively coupled tothe edge support to spin the object in a fixed plane on the back supportduring planarization, the fixed plane being substantially parallel to atreatment surface of a polishing pad.
 4. The apparatus of claim 1further comprising a drive operatively coupled to the edge support, theobject having a center axis, wherein the edge support rotates the objectabout its center axis in a fixed plane during planarization, the fixedplane being substantially parallel to a treatment surface of a polishingpad.
 5. The apparatus of claim 1 further comprising a drive operativelycoupled to the edge support to move the object laterally in a fixedplane during planarization, the fixed plane being substantially parallelto a treatment surface of a polishing pad.
 6. The apparatus of claim 5wherein the edge support moves the object in a predetermined patternrelative to the polishing pad, the pattern being in a fixed plane atleast when the polishing pad contacts the object during planarization,the fixed plane being substantially parallel to a treatment surface of apolishing pad.
 7. The apparatus of claim 6 wherein the predeterminedpattern is substantially radial.
 8. The apparatus of claim 6 wherein thepredetermined pattern is substantially linear.
 9. The apparatus of claim6 wherein the predetermined pattern is substantially continuous, whereinthe object moves laterally in a fixed plane during a planarizationprocess.
 10. The apparatus of claim 6 wherein the predetermined patternis substantially discontinuous, wherein the object moves laterally in afixed plane during planarization when the polishing pad contacts theobject.
 11. The apparatus of claim 1 wherein the edge support comprisesa plurality of rollers, the object and each of the rollers having acenter axis, each of the rollers being movably coupled to the edge ofthe object such that at least one of the rollers rotates about itscenter axis to drive the object to rotate about its center axis.
 12. Theapparatus of claim 11 wherein one of the rollers rotates about itscenter axis in a clockwise direction to drive the object to rotate aboutits center axis in a counterclockwise direction.
 13. The apparatus ofclaim 1 wherein the edge support rotates about the center axis of theobject thereby causing the object to rotate about the center axis. 14.The apparatus of claim 1 wherein a surface of the back support comprisesa diameter that is substantially the same size as a polishing paddiameter of a polishing pad for providing adequate support to the objectduring planarization.
 15. The apparatus of claim 1 wherein the backsupport comprises an air bearing.
 16. The apparatus of claim 1 whereinthe back support is a liquid bearing.
 17. The apparatus of claim 1wherein the back support tracks a polishing pad to provide support tothe object during planarization.
 18. The apparatus of claim 1 furthercomprising a polishing head and a base, wherein the back support and thepolishing head operatively couple to the base, the polishing headcomprising a polishing pad, the base being configured such that thesurface of the back support is substantially planar with the polishingpad, wherein the back support tracks the polishing pad to providesupport to the object during planarization.
 19. The apparatus of claim 1further comprising a carousel having a plurality of edge supports forhandling a plurality of objects.
 20. A chemical-mechanical planarizationapparatus for planarizing an object, the apparatus comprising: an edgesupport movably coupled to an edge of an object for supporting andpositioning the object during planarization; a back support operativelycoupled to the edge support, the back support having at least onesurface for supporting the back side of the object, the surfaceproviding a substantially friction free interface between the surfaceand the back side of the object to allow the object to move across thesurface of the back support; and a polishing head operatively coupled tothe back support, the polishing head comprising a polishing pad, thepolishing pad having a treatment surface and a center axis, thepolishing head being rotatably coupled to a drive motor to rotate thetreatment surface about the center axis to polish the object, thepolishing pad and the back support being disposed on opposite sides ofthe object and being generally aligned with one another.
 21. Theapparatus of claim 20 wherein the polishing pad comprises a diameterthat is substantially less than a diameter of the object.
 22. Theapparatus of claim 20 wherein the back support tracks the polishing padto provide support to the object during planarization.
 23. The apparatusof claim 20 wherein the base is a dual arm, the dual arm comprises afirst arm and a second arm, wherein the polishing head attaches to thefirst arm and the back support attaches to the second arm, wherein theback support tracks the polishing pad to provide support to the objectduring planarization.
 24. The apparatus of claim 23 wherein the firstarm and second arm extend telescopically to traverse the pad laterallyacross the wafer during planarization.
 25. The apparatus of claim 23wherein the first arm and the second arm are movable independently ofone another.
 26. The apparatus of claim 23 wherein the dual armcomprises a C-shaped member having projected gimbal points on oppositesides of the wafer, the first arm movably supporting a firsthemispherical member having a first projected gimbal point at or nearthe upper surface of the wafer, the second arm movably supporting asecond hemispherical member having a second projected gimbal point at ornear the lower surface of the wafer.
 27. The apparatus of claim 20wherein the polishing head moves laterally across the wafer duringplanarization in a predetermined pattern in a fixed plane substantiallyplanar to the wafer.
 28. The apparatus of claim 20 wherein the polishinghead is rotatable about an axis of the polishing pad to spin thepolishing pad around the axis of the polishing pad.
 29. The apparatus ofclaim 20 wherein the polishing head is rotatable about an offset axisspaced from an axis of the polishing pad to orbit the polishing padaround the offset axis.
 30. A chemical-mechanical planarizationapparatus for planarizing an object, the apparatus comprising: apolishing head comprising a polishing pad, the polishing pad beingrotatably coupled to a drive motor to move a treatment surface of thepolishing pad about a center axis for a chemical mechanicalplanarization operation of a face of a wafer; a back support operativelycoupled to the polishing head, the back support comprising at least onesupport member for supporting the wafer, the member comprising an uppersurface to support a back side surface of the wafer; and a drive coupledto an edge of the object to rotate the object on the back support abouta fixed plane, the fixed plane being substantially parallel to thetreatment surface of the polishing pad; wherein the upper surfaceprovides a substantially friction free interface between the uppersurface and the back side surface of the object to allow the object tomove across the upper surface; wherein the back support and thepolishing head are operatively coupled to a base, the base beingconfigured such that the surface of the back support is substantiallyplanar with the polishing pad, wherein the back support tracks thepolishing pad to provide support to the object during planarization.